1. Field of the Invention
The present invention is related to tools which are used for tightening and loosening uniquely formed nuts, such as tapered nuts, for the purpose of preventing crimes and, in particular, tools for tightening and loosening a conical, trapezoidal shaped security nut, and to the security nut associated with the tools.
2. Description of the Prior Art
The traditional head of the bolt and the nut, which are used for tightening, are typically hexagonal or multiple-sided in shape so that an ordinary person can tighten them using a tool easily available in the open market, such as a spanner or a monkey wrench. Therefore, pranks and crimes have begun to occur more frequently, such as removing the tightening section of a railroad as a prank or stealing an automatic vending machine by removing the fasteners.
To resolve these problems, Japanese Patent Publication #2000-205225 (to Tokkai), for example, discloses bolts and nuts that cannot easily be loosened or removed by an ordinary person. The head of the bolt and the nut are shaped as a multi-sided or non-arcing outer rim, while the surface of the outer rim is sloped and flared from the top toward the bottom. If these bolts and nuts are tightened using the special tightening tool that has a sloped wall in order to make contact with the sloped surface of the bolt or the nut, then these bolts and nuts cannot be removed using an ordinary tool available in the open market because ordinary tools cannot grip the sloped outer rim, and therefore crime can be prevented from occurring.
In the invention described in the aforementioned publication, the rotational torque for tightening is transmitted only by engaging the sloped wall of the dedicated tightening tool with the sloped surface of the bolt and nut. Therefore, in order for the bolt and nut to engage the dedicated tightening tool, the outer rims of the bolt and nut must be shaped as multi-sided or non-arcing. However, it is preferable to make the shape a conical trapezoid because this shape is most difficult to rotate and thus the most effective in terms of crime prevention. However, with the conical trapezoid shape there is a problem in which the aforementioned dedicated tightening tool cannot be engaged, meaning that the bolt and nut cannot be rotated. Moreover, a complex manufacturing process is required for production of the multi-sided shape, which is impractical due to the high costs of labor and production.
Even though security has to be improved, sometimes the nuts and bolts must be removed, such as when there is a need to relocate an automatic vending machine. When removing the nuts, much greater torque is required for loosening than tightening. However, the process of removal has never been considered in the design of the nuts or in regard to the dedicated tightening tool described in the aforementioned publication. Thus there is a problem in which the removal of nuts is quite difficult due to poor torque transmittal.
Furthermore, to improve security it must be difficult to remove the nuts using other common tools such as pliers, in addition to a spanner or a monkey wrench, both of which are commonly used to tighten and loosen ordinary nuts.
What is thus desired is to provide a dedicated tool for tightening the security nut, a tool for loosening the security nut, a tool for tightening/loosening the security nut, and the security nut associated with these tools that will allow easy tightening of the security nut, make it difficult to remove the security nut when using ordinary tools, and making it easy to remove the security nut if the dedicated tool is used.